Session: Wednesday Morning, June 18

Time: 9:50

Two issues will be reviewed: (1) combined effects of noise and aging on
hearing and (2) protective effects of calcium-channel blockers (CCBs). There are
no empirical data on the auditory effects of noise exposure and the aging
process in humans. The only sources of information on combined effects of noise
and age have been epidemiological studies. In recent experiments, gerbils were
exposed monaurally at middle age to an intense tone which caused approximately
20 dB of noise-induced permanent threshold shift (NIPTS). At 36 months (lifespan
of the gerbil), the threshold in the unexposed ear was considered the
age-related loss and that in the exposed ear was considered the loss caused by
aging plus noise. Data were examined in terms of published models which attempt
to discriminate between NIPTS and presbycusis in older individuals. Most models
significantly overestimated the noise-induced component of the hearing loss in
the aged subjects. In the second series of experiments, gerbils were exposed to
an intense noise while concurrently receiving CCBs or placebos. Nimodipine (a
potent CCB) reduced the NIPTS. Furthermore, epidemiological data suggest that
aged women taking CCBs have hearing levels 10--12 dB better than average. [Work
supported by NIH-NIDCD and NOHR.]